Various studies have been conducted for error correction. For example, in a type of error correction code, a check bit for error correction is calculated by using exclusive OR operation. Meanwhile, in other kind of error correction code, more complicated operations are used. The error correction may be applied to various applications, for example, a multicast distribution system.
As techniques to correct an error caused at data transmission, for example, a Forward Error Correction (FEC) and an Automatic Repeat-reQuest (ARQ) are known.
The FEC adds redundancy to data to be transmitted. Several techniques are proposed that take account of a balance between redundancy and efficiency.
For example, Japanese Laid-open Patent Publication Nos. Sho. 63-234632 and 2010-74595 discuss data transmission methods that aim to achieve an appropriate error correction control without deteriorating data transmission efficiency.
Japanese Laid-open Patent Publication No. 2004-254127 that the disclosure includes receiving a NACK (negative acknowledgement) indicating there is a lost packet that may not be recovered by FEC from a reception device. Moreover, the disclosure includes redundant data amount adjustment operation to adjust amount of redundant data depending on a reception status of NACK (or identification information of a lost packet included in the NACK).
Furthermore, Japanese Laid-open Patent Publication No. 2004-254127 discusses that the disclosure includes a transmission speed control operation to adjust the number of packets to be transmitted per hour according to the amount of redundant data adjusted at the redundant data amount adjustment operation. Moreover, the disclosure includes an operation to adjust a shuffling span according to a reception status of NACK and an operation to adjust a packet size according to a reception status of NACK.
A method is proposed in order to efficiently calculate error correction data as will be described below. In other words, Japanese Laid-open Patent Publication No. 2006-067072 discusses that when error correction data to be inserted into transmission data at specific intervals is generated by calculating exclusive-OR of the transmission data, the exclusive-OR is continuously calculated cumulatively independent of the insertion intervals. Exclusive-OR between a calculated value of the exclusive-OR at the time of the previous error correction data insertion and a calculated value of the exclusive-OR at the time of the current error correction data insertion is calculated, and error correction data to be inserted at the present time is generated by the calculated exclusive-OR.
A transmission rate control method using an error correction packet is also proposed. Japanese Laid-open Patent Publication No. 2006-345523 discusses that the disclosure includes an operation to transmit a first packet group that is made up of data packets and error correction packets with a certain ratio to a reception device. Moreover, the disclosure includes an operation to transmit a second packet group in which a ratio of error correction packets is adjusted by feedback information related to the first packet group. Furthermore, the disclosure includes an operation to adjust a transmission rate by feedback information related to the second packet group.
Japanese Laid-open Patent Publication No. 2007-251737 discusses a communication system to improve a decoding success rate by making RPS dynamically respond to a communication status. The communication system transfers data through a transmission route between a transmission side device and a reception side device.
The above-described transmission-side device includes an encoding device that generates data that is obtained by redundantly encoding original data, a transmission device that transmits data encoded by the encoding device to a transmission route, and an encoding rate determination device that sets and controls an encoding rate in the encoding device. Moreover, the reception side device includes a reception device that receives encoded data transmitted through the transmission route, a decoding device that decodes original data from received encoded data, and a loss rate assumption device that measures a loss rate on a route of transmitted encoded data. The encoding rate determination device of the transmission-side device changes and controls an encoding rate at the encoding device based on an obtained loss rate.